Grating filtering substrate integrated waveguide slot array antenna and design method thereof

Abstract

The invention provides a grating filtering substrate integrated waveguide slot array antenna and a design method thereof. A radiation slot array antenna is formed by arranging a radiation slot array on a first metal layer on the surface of a substrate integrated waveguide; and secondly, a grating filtering structure is formed by periodically arranging metalized blind hole groups at the bottom of the substrate integrated waveguide, so that a stop band is created in a traveling wave area, a signal filtering and shielding effect is realized in a specific frequency band, the miniaturization of the antenna is realized, the connection loss caused by additionally connecting a filter is avoided, and the efficiency of the antenna is improved. According to the grating filtering substrate integrated waveguide slot array antenna, the selection and propagation of a specific working frequency band are realized by controlling the aperture of the metalized blind hole, the hole pitch of the metalized blind hole group, the line pitch, the waveguide shape and the opening shape of the radiation slot array in the grating filtering substrate integrated waveguide slot array antenna; and the signal anti-interference performance of the grating filtering substrate integrated waveguide slot array antenna is simply and conveniently improved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic radiation technology, and more specifically, to a design method for a grating filter substrate integrated waveguide slot array antenna. Background Art

[0002] Antennas are essential components of wireless communication systems as basic devices for receiving and transmitting radio waves. Among them, substrate integrated waveguide (SIW) is a planar waveguide structure first proposed at the beginning of this century. Its transmission characteristics are equivalent to the transmission performance of dielectric-filled rectangular waveguides. Its structure is to arrange two rows of parallel metallized through holes on a dielectric substrate and cover the top and bottom of the dielectric substrate with metal layers. Comparing the two, substrate integrated waveguide can greatly reduce the processing cost and design complexity, and is easy to integrate with other active or passive devices in the current communication system. At the same time, there will be no transmission loss and mutual coupling problems at high frequencies. Therefore, it has become a widely used planar waveguide transmission line. Substrate integrated waveguide transmission lines have the advantages of low loss, low cost, high power capacity and easy integration, and have become a hot spot in the design of mobile satellite communication antennas in recent years. Antennas based on substrate integrated waveguide design have the advantages of low profile, small size, high power capacity and easy integration. Due to the long distance between the satellite and the ground, the transmit power requirement of the transmitting RF front end is large, which will inevitably cause interference to the receiving RF front end. To solve this problem, a common method is to use an additional microwave filter cascaded to the RF link. This solution is effective, but requires additional space for the filter and also introduces connection losses, which affects the miniaturization and efficiency of the system. Summary of the invention The present invention aims to overcome at least one of the shortcomings of the above-mentioned prior art and provides a design method for a grating filter substrate integrated waveguide slot array antenna, which simultaneously loads the waveguide slot array antenna and the grating filter structure in the same substrate integrated waveguide, thereby improving the miniaturization and efficiency of the antenna designed based on the substrate integrated waveguide.

[0003] An object of the present invention is to provide a grating filter substrate integrated waveguide slot array antenna, comprising an array antenna structure and a grating filter structure integrated in the same substrate integrated waveguide, the array antenna structure comprising a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a metal floor arranged in a stacked manner, and also comprising metallized vias and radiation slots arranged in an array, the metallized vias connecting the first metal layer, the first dielectric layer, the second dielectric layer and the metal floor, the metallized vias are arranged at intervals to form two rows of metallized via groups arranged in parallel, and the metallized via groups are used as the long side of the substrate integrated waveguide; the radiation slots are opened on the first metal layer and arranged longitudinally along the wide side direction of the substrate integrated waveguide; The grating filter structure includes a plurality of metallized blind holes, which are arranged at intervals to form a plurality of metallized blind hole groups, and the metallized blind hole groups are periodically loaded on the bottom of the array antenna structure to form a grating; the metallized blind holes are connected to the second dielectric layer and the metal floor; the metallized blind hole groups are opened between two rows of metallized vias and distributed along the wide side direction of the waveguide.

[0004] In this technical solution, by integrating the Bragg grating filter structure and the radiating slot array antenna in the same substrate integrated waveguide, a compact filter antenna is formed, which not only realizes the miniaturization of the antenna, but also avoids the connection loss of the additional connection filter, thereby improving the efficiency of the antenna. Among them, the substrate integrated waveguide is connected to the first metal layer and the metal floor by two layers of dielectric layers, and two rows of metallized through-hole groups are opened on both sides of the substrate integrated waveguide to connect the first metal layer and the metal floor, so that the input signal can enter from the wide side of the substrate integrated waveguide and propagate along the long side direction. Specifically, a radiation slot array is provided on the first metal layer, and the radiation slots are provided between two rows of metallized vias and arranged longitudinally along the wide side direction of the substrate integrated waveguide, so as to generate a specific radiation mode and directivity diagram in the substrate integrated waveguide, thereby forming a radiation slot array antenna; secondly, a grating filter structure is formed at the bottom of the substrate integrated waveguide by periodically providing a group of metallized blind holes connecting the metal floor and the second dielectric layer at the bottom of the substrate integrated waveguide, thereby creating a stopband in the traveling wave region of the substrate integrated waveguide. When the signal enters the substrate integrated waveguide, if the input signal propagates in the passband, the propagation loss of the input signal in the traveling wave region is extremely small, so that the signal can be radiated normally from the radiation slot, but when the input signal propagates in the stopband, the energy of the signal will experience a significant attenuation in the waveguide, so that only a small amount of signal can be radiated from the radiation slot with low radiation resonance, thereby achieving a good signal filtering and shielding effect.

[0005] Another object of the present invention is to provide a design method for a grating filter substrate integrated waveguide slot array antenna, which specifically comprises the following steps: S1. Determine the target reflection spectrum required by the grating filter structure, and according to the required target reflection spectrum, obtain the refractive index modulation of the grating filter structure by iterative calculation based on the IS technology of the LP algorithm, and determine the local period Λ of the grating according to the Bragg condition; S2. adjusting the amplitude △a of the grating teeth according to the bandwidth △λ and the coupling coefficient k filtered by the grating filter structure; S3 determines the cross-sectional dimensions of the substrate integrated waveguide, including the width a and height b of the waveguide, the diameter and spacing of the metallized vias; S4. Determine the width △L of the grating teeth of the grating filter structure, and the width △L of the grating teeth for the spacing, height and diameter of the metallized vias respectively; S5. Calculate the length of the radiation slot array and the shape of the radiation slot according to the beam width and gain requirements, including the slot length, width, spacing, number of slots, and position offset.

[0006] In the technical solution of the present application, the target working frequency band of the grating filter substrate integrated waveguide slot array antenna is determined by the transmission frequency band of the radiating slot array and the selected frequency band of the grating filter structure. Therefore, when designing the grating filter substrate integrated waveguide slot array antenna, it is necessary to first determine the target reflection spectrum of the array antenna, and firstly design the parameters of the grating filter structure according to the target reflection spectrum, so that the refractive index modulation degree of the grating filter structure is adapted to the target reflection spectrum. Specifically, the design of selective filtering for the target working frequency band can be achieved by controlling the aperture of the metallized blind hole, the hole spacing and the row spacing of the metallized blind hole group; further, by setting the shape of the waveguide and the opening shape of the radiating slot array, including the length and width of the radiating slot and the setting length of the radiating slot array to be adapted to the target reflection spectrum, the selection and propagation of a specific working frequency band are realized in the grating filter substrate integrated waveguide slot array antenna, and the signal anti-interference performance of the grating filter substrate integrated waveguide slot array antenna is simply and conveniently improved.

[0007] Specifically, in step S1, after determining the target reflection spectrum required by the grating filter structure, and according to the required target reflection spectrum, the IS technology based on the LP algorithm is adopted, and the target characteristic curve is set by utilizing the causal relationship between the grating filter structure parameters, that is, the apodization function and the local chirp amount, and the required target reflection spectrum. Starting from the target characteristic curve, the coupling coefficient k of the grating is inverted and calculated, and then the grating filter structure is determined by the relationship between the coupling coefficient and the apodization function and the local chirp amount distribution. The specific formula is as follows: (3) (4) (5) (6) (7) Among them, ρ j Characterizes the pulse effect of the jth reflector at time t = 0, that is, the time-domain reflection coefficient; (Equation 4) reflects ρ j The relationship between the coupling coefficient of the j-th grating, where q j * Q j The conjugate complex number of; Formula (5) is the iterative formula of the frequency domain reflection coefficient, where r1(λ) is required to be the physically achievable target reflection coefficient, which is obtained by windowing and apodizing the ideal target spectrum r(λ). The design can refer to the window function design idea in the finite length unit impulse response (FIR) digital filter design method; In Formula (6), ∆n0(z) is the refractive index modulation amplitude, and θ(z) is the grating phase; In Formula (7), Λ(z) is the grating chirp function to be determined; The iterative process from the physically achievable target reflection spectrum to the grating filter structure is as follows: A1. Write down the expression of physically achievable target spectrum r1(λ) according to the design requirements and discretize it; A2. Let j = 1; A3. Calculate ρ from formula (3) j , and then calculate q according to formula (4) j , r is calculated by formula (5) (j+1) (λ); A4. Set j=j+1 and repeat step A3 until all q are calculated. j ; Then determine the refractive index modulation and local chirp distribution of the grating filter structure.

[0008] Further, in step A1 of the iteration process, the method for determining the physically achievable target spectrum r1(λ) is as follows: determining the target reflection spectrum of the grating filter structure according to the requirements, and performing windowing and apodization on the target reflection spectrum of the grating filter structure so that the impulse response outside the window is zero, and shifting the entire impulse response so that it is excited at t=0, thereby obtaining the physically achievable target spectrum r1(λ); In the technical solution, a uniform comb-shaped grating filter structure is formed in the substrate integrated waveguide by setting a number of metallized blind holes. Accordingly, preferably, in one embodiment of the technical solution, the various indicators of the target reflection spectrum of the grating filter structure are designed as follows: peak reflectivity 0.95, -0.5dB bandwidth 1Ghz:, -30dB bandwidth is 1.5Ghz, reflection peaks are arranged with equal intensity and equal spacing, and when the reflection coefficient amplitude angle is zero, the physically achievable target spectrum r1(λ) of the ideal comb-shaped grating filter structure can be expressed by a super-Gaussian function as follows: (8); Among them, n eff is the average effective refractive index of the grating filter structure; j is the central wavelength of the grating filter structure.

[0009] Further, in step S2, the metallized blind holes form a uniform grating filter structure. When the grating teeth formed by the metallized blind holes are regarded as rectangles, the perturbation of the dielectric constant caused by the grating filter structure is expressed as: (9); Performing Fourier transform on the rectangular function of equation (9) and taking the first order q=1, we can obtain: (9-1); Where α is the duty cycle of the grating, which ranges from 0.01 to 0.5. According to the mode orthogonal normalization condition, the coupling coefficient k of the uniform grating is obtained by combining equations (9) and (9-1), which is expressed as: (10); Where △n is the refractive index modulation of the grating filter structure, Λ is the local chirp distribution, and λ B is the reflection center wavelength of the grating filter structure, that is, the Bragg wavelength, n eff is the average value of the effective refractive index of the grating filter structure; The relationship between the coupling coefficient k of the grating and the amplitude △a of the grating teeth is expressed by the empirical formula: (11).

[0010] Furthermore, in step S3, the substrate integrated waveguide includes a dielectric substrate formed by a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a metal floor, and a side metal wall formed by two rows of metallized vias. Compared with a traditional metal waveguide, the length L and width a of the equivalent waveguide for substantially transmitting signals on the substrate integrated waveguide are the same as the length L of the substrate integrated waveguide. SIW and width W SIW The equivalent relationship between them is: (12); Wherein, d represents the diameter of the metallized via hole, and p represents the distance between adjacent holes of the metallized via hole; And because the sidewalls of the substrate integrated waveguide are two rows of metallized vias with gaps, in some special cases, the energy in the waveguide will leak out from the gaps. From the perspective of energy leakage, in order to reduce the radiation loss of energy in the waveguide, the smaller the metallized via spacing, the better. However, from the perspective of practical engineering, the smaller the spacing, the higher the requirements for processing technology, and the more difficult the engineering will be. Therefore, in order to ensure the normal transmission of energy in the waveguide and taking into account the difficulty of process processing, the metallized via diameter d and center distance p usually need to meet the following relationship conditions: d<p <2d(13-1); 0.05λ0<p<0.25λ0(13-2); Where λ0 is the center wavelength of the target operating frequency of the waveguide.

[0011] Furthermore, in step S4, the width of the grating teeth of the grating filter structure is ΔL = a*beta, and beta is a constant with a value between 0.01 and 0.5.

[0012] Further, in step S5, the length of the radiation slot array is calculated according to the lobe width and gain requirements. Specifically, the length of the radiation slot array is consistent with the length L of the waveguide. At this time, the calculation formula is: (14); Where, σ is the broadening factor of the Tailao line source; R0 is the ratio of the main lobe to the side lobe level; Specifically, the Tailao line source broadening factor σ is determined by the following formula: (15); in, It is the dividing point between the equal side lobe area and the unequal side lobe area of ​​the radiation pattern; A is determined by the ratio R0 of the level of the antenna main lobe and the side lobe: (16); Then, the total number of slots N is calculated from the length L of the radiation slot array and the slot spacing Ls of the radiation slot array: N = (L / Ls) - 1 (17); Furthermore, the slot spacing Ls, slot length Lslot, and slot width Wslot of the radiation slot array satisfy the following relationship: Ls=2 / 3 (18-1); 200 (18-2); Lslot=0.96 / 2(18-3).

[0013] Furthermore, the radiation slot array adopts a non-resonant waveguide slot array, the radiation slots are arranged longitudinally in the wide side direction of the waveguide, and adjacent radiation slots in the radiation slot array have a certain offset in the wide side direction of the waveguide, and the offset distance satisfies the Taylor weighted form.

[0014] Specifically, when the radiation slot array satisfies the Taylor array, the excitation amplitude of each unit of the Taylor array is: (19); Where: (20) ; (twenty one); After normalizing the excitation amplitude, since the characteristics of the non-resonant waveguide slot array are that one end of the waveguide is terminated with a matching load, the slot is resonant, the transmission attenuation of the waveguide is ignored, and the waveguide is matched over the entire length, the conductance value of each radiation slot can be obtained by the following formula: (twenty two); Where P(p) is the power radiated per unit length of the slot, which is proportional to the square of the field distribution amplitude at that location; P0(p) is the input power in the waveguide, and p is the coordinate of the midpoint of the radiation slot; When the antenna input power is 1, the power absorbed by the terminal load is r, then: (twenty three); Thus, the conductivity value of each radiation gap can be obtained; When the conductance value of each radiating slot is determined, the normalized equivalent conductance of the broadside longitudinal resonant slot (23) is substituted into the following formula to calculate the distance x that each radiating slot deviates from the center line of the broadside of the waveguide: (twenty four) in, (twenty four), Right now, (25).

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. A grating filter substrate integrated waveguide slot array antenna is provided, which integrates a Bragg grating filter structure and a radiation slot array antenna in the same substrate integrated waveguide. Specifically, a radiation slot array is provided on a first metal layer, and the radiation slots are arranged between two rows of metallized vias and arranged longitudinally along the wide side direction of the substrate integrated waveguide, so as to generate a specific radiation mode and directivity diagram in the substrate integrated waveguide, thereby forming a radiation slot array antenna; secondly, a grating filter structure is formed at the bottom of the substrate integrated waveguide by periodically arranging a group of metallized blind holes connecting a metal floor and a second dielectric layer at the bottom of the substrate integrated waveguide, thereby creating a stop band in the traveling wave region of the substrate integrated waveguide, thereby achieving a good signal filtering and shielding effect in the corresponding frequency band of the grating filter structure; by forming a compact filtering antenna array, the miniaturization of the antenna is achieved, and the connection loss of the additional connection filter is avoided, thereby improving the efficiency of the antenna.

[0016] 2. A design method for a grating filter substrate integrated waveguide slot array antenna is provided, wherein the target operating frequency band of the grating filter substrate integrated waveguide slot array antenna is determined by the transmission frequency band of the radiation slot array and the selection frequency band of the grating filter structure. In the design in which the refractive index modulation degree of the grating filter structure is adapted to the target reflection spectrum, specifically, the design of selective filtering for the target operating frequency band can be achieved by controlling the aperture of the metallized blind hole, the hole spacing and the row spacing of the metallized blind hole group; secondly, by setting the shape of the waveguide and the opening shape of the radiation slot array, including the length and width of the radiation slot and the setting length of the radiation slot array to be adapted to the target reflection spectrum, the selection and propagation of a specific operating frequency band are achieved in the grating filter substrate integrated waveguide slot array antenna, and the signal anti-interference performance of the grating filter substrate integrated waveguide slot array antenna is simply and conveniently improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the principle of grating filtering.

[0018] Figure 2 Schematic diagram of the principle of waveguide grating filtering structure.

[0019] Figure 3 A schematic flow chart of a design method for a grating filter substrate integrated waveguide slot array antenna provided by the present invention.

[0020] Figure 4 This is one of the structural schematic diagrams of a grating filter substrate integrated waveguide slot array antenna provided by the present invention.

[0021] Figure 5 The second structural schematic diagram of a grating filter substrate integrated waveguide slot array antenna provided by the present invention.

[0022] Figure 6 A schematic diagram of a grating filter substrate integrated waveguide slot array antenna provided by the present invention in which the signal is located within the passband of the grating filter structure.

[0023] Figure 7 A schematic diagram of a grating filter substrate integrated waveguide slot array antenna provided by the present invention in which a signal is located within the pass resistance of a grating filter structure.

[0024] Figure 8 It is a schematic diagram comparing the reflection coefficients of the filtering antenna provided in Comparative Example 1 of the present invention and the ordinary antenna within the working frequency.

[0025] Fig. 9 It is a schematic diagram comparing the antenna gain within the working frequency of the filtering antenna provided in Comparative Example 1 of the present invention and the common antenna.

[0026] Fig.10 This is a schematic diagram comparing the efficiencies of the filter antenna and the common antenna provided in Comparative Example 1 of the present invention at 12.25-12.75 GHz.

[0027] Fig.11 The radiation patterns of the filter antenna and the common antenna provided in Comparative Example 1 of the present invention at 12.25 GHz, 12.5 GHz and 12.75 GHz.

[0028] Description of the drawings: first metal layer 1, first dielectric layer 2, second metal layer 3, second dielectric layer 4, metal floor 5, metallized via 6, radiation gap 7, metallized blind hole 8. DETAILED DESCRIPTION

[0029] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0030] In the field of optical fiber communication, waveguide grating filter is a very important device. As a kind of periodic dielectric waveguide, the waveguide grating filter structure has periodic dielectric perturbations in the propagation direction of the light mode. When the spatial periodic refractive index changes, some frequency signals will be reflected. When the grating period is about half of the wavelength of the incident signal, all reflected waves are coherently combined into a large reflection with a specific wavelength. This is called the Bragg condition. The wavelength at which the incident wave is reflected is called the Bragg wavelength. Optical signals of other wavelengths are almost unaffected by the Bragg grating and will continue to be transmitted through the grating.

[0031] like Figure 1As shown, when the wave propagates through the grating, there is almost no signal attenuation or signal change. Only the wavelength that meets the Bragg condition will be affected and produce strong reflection. Therefore, the present invention introduces the Bragg waveguide grating (Bragg Wave-guide Grate, BWG) structure in the microwave and millimeter wave field, and through precise grating design, the basic characteristics and advantages of Bragg waveguide grating (BWG) filtering are demonstrated in the microwave and millimeter wave field.

[0032] like Figure 2 As shown, when a periodic Bragg grating filter structure is introduced into the waveguide, due to the change in the effective refractive index of the waveguide, there is reflection on each interface, and the phase change of the reflected wave is determined by the wavelength λ and the period Λ. Ultimately, the reflected light within a certain wavelength range is coherent and constructive, achieving filtering. At other wavelengths, multiple reflections are coherent and destructive, and as a result, the signals of these wavelengths continue to propagate in the original direction through the grating area.

[0033] In such Figure 2 In the waveguide grating filter structure shown in the figure, the reflection center wavelength is called the Bragg wavelength, denoted by λ B ,λ B The Prague conditions are met: (1), Where Λ is the grating period and neff is the average value of the mode effective refractive index, that is: (2), Specifically, in the waveguide grating filter structure, one period consists of two parts. The waveguides of these two parts are symmetrical about the waveguide center with a width of W. The widths are W+△W and W-△W respectively, and their mode effective refractive indices correspond to n eff1 and n eff2 In this structure, for different grating tooth amplitudes △W (corrugation width), the average value neff of the effective refractive index of the grating part mode does not change much, and is approximately the effective refractive index of the waveguide width W. Therefore, it can be seen that the central wavelength of the waveguide grating filter structure has no offset.

[0034] Example 1 like Figure 3-7As shown, this embodiment provides a grating filter substrate integrated waveguide slot array antenna, including an array antenna structure and a grating filter structure integrated in the same substrate integrated waveguide, the array antenna structure includes a first metal layer 1, a first dielectric layer 2, a second metal layer 3, a second dielectric layer 4 and a metal floor 5 arranged in a stacked manner, and also includes an array of metallized vias 6 and radiation slots 7, the metallized vias 6 connecting the first metal layer 1, the first dielectric layer 2, the second dielectric layer 4 and the metal floor 5, the metallized vias 6 are arranged at intervals to form two rows of metallized vias 6 groups arranged in parallel, and the metallized vias 6 groups are used as the long side of the substrate integrated waveguide; the radiation slot array is opened on the first metal layer 1, and is arranged longitudinally along the wide side direction of the substrate integrated waveguide; The grating filter structure includes a plurality of metallized blind holes 8, which are arranged at intervals to form a plurality of metallized blind hole 8 groups, and the metallized blind hole 8 groups are periodically loaded on the bottom of the array antenna structure to form a grating; the metallized blind holes 8 are connected to the second dielectric layer 4 and the metal floor 5; the metallized blind hole 8 groups are opened between two rows of metallized vias 6 and distributed along the wide side direction of the waveguide.

[0035] Specifically, the substrate integrated waveguide is connected to the first metal layer 1 and the metal floor 5 by two dielectric layers, and two rows of metallized through-hole groups are opened on both sides of the substrate integrated waveguide to connect the first metal layer 1 and the metal floor 5, so that the input signal can enter from the wide side of the substrate integrated waveguide and propagate along the long side. Specifically, by opening a radiation slot array on the first metal layer 1, and the radiation slot 7 is arranged between the two rows of metallized through-holes 6, and arranged longitudinally along the wide side direction of the substrate integrated waveguide, a specific radiation mode and directional pattern are generated in the substrate integrated waveguide, forming a radiation slot array antenna; preferably, the radiation slot array adopts a non-resonant waveguide slot array, the radiation slots 7 are arranged longitudinally in the wide side direction of the waveguide, and the adjacent radiation slots 7 in the radiation slot array have a certain offset in the wide side direction of the waveguide, and the offset distance satisfies the Taylor weighting form, thereby improving the directivity of the radiation slot array antenna and optimizing the gain and bandwidth of the antenna.

[0036] Secondly, if Figure 6-7As shown, a grating filter structure is formed at the bottom of the substrate integrated waveguide by periodically setting a group of metalized blind holes 8 connecting the metal floor 5 and the second dielectric layer 4 at the bottom of the substrate integrated waveguide, thereby creating a stopband in the traveling wave region of the substrate integrated waveguide. When the signal enters the substrate integrated waveguide, if the input signal propagates in the passband, the propagation loss of the input signal in the traveling wave region is extremely small, so that the signal can be radiated normally from the radiation slot 7, but when the input signal propagates in the stopband, the energy of the signal will experience a significant attenuation in the waveguide, so that only a small amount of signal can be radiated from the radiation slot 7 with low radiation resonance, thereby achieving a good signal filtering and shielding effect. By integrating the Bragg grating filter structure and the radiation slot array antenna in the same substrate integrated waveguide, a compact filtering antenna is formed, which not only realizes the miniaturization of the antenna, but also avoids the connection loss of the additional connection filter, thereby improving the efficiency of the antenna.

[0037] Example 2 This embodiment provides a design method for a grating filter substrate integrated waveguide slot array antenna, which specifically includes the following steps: S1. Determine the target reflection spectrum required by the grating filter structure, and according to the required target reflection spectrum, obtain the refractive index modulation of the grating filter structure by iterative calculation based on the IS technology of the LP algorithm, and determine the local period Λ of the grating according to the Bragg condition; S2. adjusting the amplitude △a of the grating teeth according to the bandwidth △λ and the coupling coefficient k filtered by the grating filter structure; S3 determines the cross-sectional dimensions of the substrate integrated waveguide, including the width a and height b of the waveguide, the diameter and spacing of the metallized vias; S4. Determine the width △L of the grating teeth of the grating filter structure, and the width △L of the grating teeth for the spacing, height and diameter of the metallized vias respectively; S5. Calculate the length of the radiation slot array and the shape of the radiation slot according to the beam width and gain requirements, including the slot length, width, spacing, number of slots, and position offset.

[0038] In the technical solution of the present application, the target working frequency band of the grating filter substrate integrated waveguide slot array antenna is determined by the transmission frequency band of the radiating slot array and the selected frequency band of the grating filter structure. Therefore, when designing the grating filter substrate integrated waveguide slot array antenna, it is necessary to first determine the target reflection spectrum of the array antenna, and firstly design the parameters of the grating filter structure according to the target reflection spectrum, so that the refractive index modulation degree of the grating filter structure is adapted to the target reflection spectrum. Specifically, the design of selective filtering for the target working frequency band can be achieved by controlling the aperture of the metallized blind hole, the hole spacing and the row spacing of the metallized blind hole group; further, by setting the shape of the waveguide and the opening shape of the radiating slot array, including the length and width of the radiating slot and the setting length of the radiating slot array to be adapted to the target reflection spectrum, the selection and propagation of a specific working frequency band are realized in the grating filter substrate integrated waveguide slot array antenna, and the signal anti-interference performance of the grating filter substrate integrated waveguide slot array antenna is simply and conveniently improved.

[0039] Specifically, in step S1, the target characteristic curve is set by using the causal relationship between the grating filter structure parameters, i.e., the apodization function and the local chirp amount, and the required target reflection spectrum. Starting from the target characteristic curve, the coupling coefficient k of the grating is inverted and calculated, and the grating filter structure is determined by the relationship between the coupling coefficient and the apodization function and the local chirp amount distribution. The specific formula is as follows: (3) (4) (5) (6) (7) Among them, ρ j Characterizes the pulse effect of the jth reflector at time t = 0, that is, the time-domain reflection coefficient; (Equation 4) reflects ρ j The relationship between the coupling coefficient of the j-th grating, where q j * Q j The conjugate complex number of ; Formula (5) is the iterative formula of the frequency domain reflection coefficient, where r1(λ) is required to be the physically achievable target reflection coefficient, which is obtained by windowing and apodizing the ideal target spectrum r(λ); In Formula (6), ∆n0(z) is the refractive index modulation amplitude, and θ(z) is the grating phase; In Formula (7), Λ(z) is the grating chirp function to be determined; The iterative process from the physically achievable target reflection spectrum to the grating filter structure is as follows: A1. Write down the expression of physically achievable target spectrum r1(λ) according to the design requirements and discretize it; A2. Let j = 1; A3. Calculate ρ from formula (3) j , and then calculate q according to formula (4) j , r is calculated by formula (5) (j+1) (λ); A4. Set j=j+1 and repeat step A3 until all q are calculated. j ; Then determine the refractive index modulation and local chirp distribution of the grating filter structure.

[0040] Furthermore, in step A1 of the iterative process, the method for determining the physically achievable target spectrum r1(λ) is as follows: the target reflection spectrum of the grating filter structure is determined according to the design requirements, and the target reflection spectrum of the grating filter structure is windowed and cut to make the impulse response outside the window zero, and the entire impulse response is shifted so that it is excited at t=0, so as to obtain the physically achievable target spectrum r1(λ).

[0041] Further, in step S2, the metallized blind holes form a uniform grating filter structure. When the grating teeth formed by the metallized blind holes are regarded as rectangles, the perturbation of the dielectric constant caused by the grating filter structure is expressed as: (9); Performing Fourier transform on the rectangular function of equation (9) and taking the first order q=1, we can obtain: (9-1); Where α is the duty cycle of the grating, which ranges from 0.01 to 0.5. According to the mode orthogonal normalization condition, the coupling coefficient k of the uniform grating is obtained by combining equations (9) and (9-1), which is expressed as: (10); Where △n is the refractive index modulation of the grating filter structure, Λ is the local chirp distribution, and λ B is the reflection center wavelength of the grating filter structure, that is, the Bragg wavelength, n eff is the average value of the effective refractive index of the grating filter structure; The relationship between the coupling coefficient k of the grating and the amplitude △a of the grating teeth is expressed by the empirical formula: (11).

[0042] Further, in the step S3, the substrate integrated waveguide includes a dielectric substrate formed by a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a metal floor, and a side metal wall formed by two rows of metallized vias, and the length L and width a of the equivalent waveguide for substantially transmitting signals are equal to the length L of the substrate integrated waveguide.SIW and width W SIW The equivalent relationship between them is: (12); Wherein, d represents the diameter of the metallized via, p represents the distance between adjacent holes of the metallized via, and d and p satisfy the following relationship: d<p <2d(13-1); 0.05λ0<p<0.25λ0(13-2); Where λ0 is the center wavelength of the target operating frequency of the waveguide.

[0043] Furthermore, in step S4, the width of the grating teeth of the grating filter structure is ΔL = a*beta, and beta is a constant with a value between 0.01 and 0.5.

[0044] Furthermore, in step S5, the length of the radiation slot array is calculated according to the lobe width and gain requirements. Specifically, the length of the radiation slot array is the length L of the waveguide, and the calculation formula is: (14); Where, σ is the broadening factor of the Tailao line source; R0 is the ratio of the main lobe to the side lobe level; Specifically, the Tailao line source broadening factor σ is determined by the following formula: (15); in, It is the dividing point between the equal side lobe area and the unequal side lobe area of ​​the radiation pattern; A is determined by the ratio R0 of the level of the antenna main lobe and the side lobe: (16); Then, the total number of slots N is calculated from the length L of the radiation slot array and the slot spacing Ls of the radiation slot array: N = (L / Ls) - 1 (17); Furthermore, the slot spacing Ls, slot length Lslot, and slot width Wslot of the radiation slot array satisfy the following relationship: Ls=2 / 3 (18-1); 200 (18-2); Lslot=0.96 / 2(18-3).

[0045] Specifically, when the radiation slot array satisfies the Taylor array, the excitation amplitude of each unit of the Taylor array is: (19); Where: (20) ; (twenty one); After normalizing the excitation amplitude, the conductance value of each radiation gap is obtained by the following formula: (twenty two); Where P(p) is the power radiated per unit length of the slot, which is proportional to the square of the field distribution amplitude at that location; P0(p) is the input power in the waveguide, and p is the coordinate of the midpoint of the radiation slot; When the antenna input power is 1, the power absorbed by the terminal load is r, then: (twenty three); Thus, the conductivity value of each radiation gap can be obtained; When the conductance value of each radiating slot is determined, the normalized equivalent conductance of the broadside longitudinal resonant slot (23) is substituted into the following formula to calculate the distance x that each radiating slot deviates from the center line of the broadside of the waveguide: (twenty four) in, (twenty four), Right now, (25).

[0046] Example 3 like Figure 3-5 As shown, this embodiment also provides a grating filter substrate integrated waveguide slot array antenna and a design method thereof. The provided grating filter substrate integrated waveguide slot array antenna is different from that of Embodiment 1 in that the grating filter substrate integrated waveguide slot array antenna provided in this embodiment is specifically suitable for the Ku band.

[0047] When designing the structure of the grating filter substrate integrated waveguide slot array antenna, the specific steps are as follows: S1. First determine the target reflection spectrum of the grating filter structure and design the following indicators: frequency range: 12.25Ghz~12.75Ghz (λ0=24mm), antenna gain: >14dB, beam width: >6°, sidelobe suppression: >15dB, peak reflectivity: 0.95, reflection center frequency wavelength: λ B=21mm (14.25Ghz), -0.5dB bandwidth △λ: 0.5Ghz (1mm), -30dB bandwidth: 1.75Ghz (2.6mm), reflection peaks are arranged at equal intervals with equal intensity, and the reflection coefficient angle is zero. In the required grating filter substrate integrated waveguide slot array antenna, the first dielectric layer and the second dielectric layer use the same dielectric substrate, which is the commercially available Rogers RT / duroid®5880 substrate, with a relative dielectric constant of 2.2 and a loss tangent tanδ=0.0009.

[0048] According to various indicators in the target reflection spectrum of the uniform comb grating filter structure in this embodiment, the target reflection spectrum of the grating filter structure is windowed and apodized to make the impulse response outside the window zero, and the entire impulse response is shifted to be excited at t=0, and the target reflection spectrum of the ideal comb grating filter structure can be expressed by a super Gaussian function as follows: (8); The central wavelength = (23.5+j*0.16)mm, (j=1, 3,…16), ,in Take the relative dielectric constant of the dielectric substrate, that is, =2.2. Furthermore, through the iterative process calculation from the physically achievable target reflection spectrum to the grating filter structure, the local chirp distribution of the grating filter is obtained to be Λ=6mm, and the effective refractive index modulation △n is 0.4042.

[0049] S2. From equations (10) and (11), it can be known that the coupling coefficient of the grating filter structure is k = 0.0385, and the amplitude of the grating teeth is △a = 0.787 mm.

[0050] S3. In order to ensure that the spacing between the metallized vias is small enough to ensure that the radiation loss of energy in the waveguide is as small as possible, while ensuring that the process requirements are met, the W of the substrate integrated waveguide is set SIW =11mm, the height of the waveguide b=2.362mm, and the length of the waveguide a=10.62mm can be calculated by formula (12); at the same time, the requirements in formula (13) are met, and the aperture size of the metallized via d1=0.6mm and the spacing between the metallized vias s1=1mm are set.

[0051] S4. By using the waveguide length values ​​a and b determined in step S3, and by △L = a*beta, where beta is 0.085, the width △L of the grating teeth of the grating filter structure is calculated; S5. The designed antenna sidelobe level is -15dB. Considering a certain engineering margin, it is designed as -20dB. From the table, we know that A=0.912. Based on engineering experience, =5, σ=1.0869; Substituting the antenna beam width θ=6° and other parameters into formula (14), the length of the radiation slot array L=9.42 , the slot spacing of the radiation slot array is Ls=2 / 3 , The total number of slots N=13 can be calculated from the length L of the radiation slot array and the slot spacing Ls of the radiation slot array according to formula (17); from formulas (17), (18-1), (18-2), and (18-3), the slot width W_slot=0.5mm; the slot length L_slot=11.52mm; In this embodiment, the radiation slot array adopts a non-resonant waveguide slot array, the radiation slots are arranged longitudinally in the wide side direction of the waveguide, and adjacent radiation slots in the radiation slot array have a certain offset in the wide side direction of the waveguide, and the offset distance satisfies the Taylor weighted form. Combining equations (19) to (25), the offset data of each slot in the radiation slot array relative to the center line of the waveguide can be obtained as shown in the following table:

[0052] That is, in the grating filter substrate integrated waveguide slot array antenna provided in this embodiment, the thickness of the first dielectric layer h1=1.575, the thickness of the second dielectric layer h2=the grating tooth amplitude △a of the grating filter structure=0.787mm; the longitudinal spacing s1=1mm of the metallized vias that penetrate the two dielectric layers and are arranged in parallel on the side wall, and the via diameter d1=0.6mm, at this time, the spacing of the metallized vias meets the condition of being much smaller than the wavelength of the waveguide, which can effectively prevent the leakage of electromagnetic waves from the side walls, and at the same time meet the requirements of the manufacturing process. Further, the diameter d2 of the metallized blind hole=the width △L of the grating tooth=0.9mm; in order to meet formula (12) and meet the process processing requirements, the hole spacing p1=1.5mm of the metallized vias is set, and the adjacent row spacing p2 is the local chirp distribution Λ, that is, p2=Λ=6mm. At the same time, in the radiation slots set in the array, the length of the radiation slot array is L_slot=11.52mm, the slot width is W_slot=0.5mm, it is longitudinally etched on the wide side of the waveguide, the offset distance is based on the Taylor weighted offset, and the adjacent spacing of the radiation slots is about more than half of the wavelength of the central waveguide of the operating frequency, which is 16mm.

[0053] Comparative Example 1 like Figure 8-11As shown, this comparative example uses a 1×13-element grating filter substrate integrated waveguide slot array antenna (filter antenna) provided in Example 3, and a 1×13 unit wave ordinary antenna (ordinary antenna) with an operating frequency of 12.25-12.75 GHz for simulation comparison. Figure 7 The simulated reflection coefficients of the filter antenna and the normal antenna are shown in Figure 8 The antenna gain of the filter antenna and the ordinary antenna is shown in the figure. It can be seen that both antennas have good input matching in the same operating frequency band. The reflection coefficient of the filter antenna in the interference band is slightly higher than that of the ordinary antenna, but the gain of the filter antenna in the interference band is about 18dB lower than that of the ordinary antenna, showing better anti-interference ability and filtering effect. It can also be found in the figure that the gain of the filter antenna is about 0.5dB lower than that of the ordinary antenna, but this does not mean that the efficiency of the filter antenna is 0.5dB less than that of the ordinary antenna, but because the waveguide wavelength of the grating waveguide is shorter than that of the ordinary waveguide, the length of the filter antenna is shorter than that of the ordinary antenna. In order to discuss this in detail, as Fig. 9 As shown, the efficiencies of the two antennas are calculated, and the results show that both antennas have similar simulation effects, with efficiencies of about 75-85% at 12.25-12.75 GHz, and the efficiency of the filtering antenna is slightly higher than that of the ordinary antenna, indicating that although some additional insertion losses are introduced in the filtering antenna due to the metal blind holes, the surface equivalent magnetic current distribution of the filtering antenna is more uniform than that of the ordinary antenna. Although the filtering antenna fails to provide higher gain in a specific direction, it can still more effectively convert signals into radiation energy, and therefore has a higher efficiency. Fig.10 The radiation patterns of the two antennas at 12.25 GHz, 12.5 GHz and 12.75 GHz are shown, indicating that the filter antenna has a good uniformly fed linear array antenna radiation pattern that is far superior to that of ordinary antennas at 12.25 GHz, 12.5 GHz and 12.75 GHz.

[0054] Therefore, this comparative example verifies the effective integration of the slot array antenna and the grating filter structure on the grating filter substrate integrated waveguide slot array antenna. Not only is the antenna small in size and has fewer interconnections, but by loading the grating filter structure, the grating filter substrate integrated waveguide slot array antenna has better out-of-band suppression capability, lower loss and higher efficiency.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A grating filter substrate integrated waveguide slot array antenna, characterized in that: The invention comprises an array antenna structure and a grating filter structure integrated in the same substrate integrated waveguide, wherein the array antenna structure comprises a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a metal floor which are stacked, and also comprises metallized vias and radiation slots which are arranged in an array, wherein the metallized vias are connected to the first metal layer, the first dielectric layer, the second dielectric layer and the metal floor, wherein the metallized vias are arranged at intervals to form two rows of metallized via groups which are arranged in parallel, and wherein the metallized via groups are used as the long sides of the substrate integrated waveguide; and wherein the radiation slot array is provided on the first metal layer and is arranged longitudinally along the wide side direction of the substrate integrated waveguide; The grating filter structure includes a plurality of metallized blind holes, which are arranged at intervals to form a plurality of metallized blind hole groups, and the metallized blind hole groups are periodically loaded on the bottom of the array antenna structure to form a grating; the metallized blind holes are connected to the second dielectric layer and the metal floor; the metallized blind hole groups are opened between two rows of metallized vias and distributed along the wide side direction of the waveguide.

2. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 1, characterized in that: The following steps are involved: S1. Determine the target reflection spectrum required by the grating filter structure, and according to the required target reflection spectrum, obtain the refractive index modulation of the grating filter structure by iterative calculation based on the IS technology of the LP algorithm, and determine the local period Λ of the grating according to the Bragg condition; S2. adjusting the amplitude △a of the grating teeth according to the bandwidth △λ and the coupling coefficient k filtered by the grating filter structure; S3 determines the cross-sectional dimensions of the substrate integrated waveguide, including the width a and height b of the waveguide, the diameter and spacing of the metallized vias; S4. Determine the width △L of the grating teeth of the grating filter structure, and the width △L of the grating teeth for the spacing, height and diameter of the metallized vias respectively; S5. Calculate the length of the radiation slot array and the shape of the radiation slot according to the beam width and gain requirements, including the slot length, width, spacing, number of slots, and position offset.

3. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 2, characterized in that: In step S1, the target characteristic curve is set by using the causal relationship between the grating filter structure parameters, i.e., the apodization function and the local chirp, and the target reflection spectrum. Starting from the target characteristic curve, the coupling coefficient k of the grating is inverted and calculated, and the grating filter structure is determined by the relationship between the coupling coefficient and the apodization function and the local chirp distribution. The specific formula is as follows: (3) (4) (5) (6) (7) Among them, ρ j Characterizes the pulse effect of the jth reflector at time t = 0, that is, the time-domain reflection coefficient; (Equation 4) reflects ρ j The relationship between the coupling coefficient of the j-th grating, where q j * for q j The conjugate complex number of ; Formula (5) is the iterative formula of the frequency domain reflection coefficient, where r1(λ) is required to be the physically achievable target reflection coefficient, which is obtained by windowing and apodizing the ideal target spectrum r(λ); In Formula (6), ∆n0(z) is the refractive index modulation amplitude, and θ(z) is the grating phase; In Formula (7), Λ(z) is the grating chirp function to be determined; The iterative process from the physically achievable target reflection spectrum to the grating filter structure is as follows: A1. Write down the expression of physically achievable target spectrum r1(λ) according to the design requirements and discretize it; A2. Let j = 1; A3. Calculate ρ from formula (3) j , and then calculate q according to formula (4) j , r is calculated by formula (5) (j+1) (λ); A4. Set j=j+1 and repeat step A3 until all q are calculated. j ; Then determine the refractive index modulation and local chirp distribution of the grating filter structure.

4. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 3, characterized in that: In the step A1, a uniform comb-shaped grating filter structure is formed through the metallized blind holes, a target reflection spectrum of the grating filter structure is determined according to requirements, and the target reflection spectrum of the grating filter structure is windowed and apodized to make the impulse response outside the window zero, and the entire impulse response is shifted to be excited at t=0, so as to obtain a physically achievable target spectrum r1(λ); The physically achievable target spectrum r1(λ) of the comb-shaped grating filter structure is expressed by a super-Gaussian function as follows: (8)； Among them, n eff is the average effective refractive index of the grating filter structure; j is the central wavelength of the grating filter structure.

5. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 2, characterized in that: In step S2, the metallized blind holes form a uniform grating filter structure. When the grating teeth formed by the metallized blind holes are regarded as rectangles, the perturbation of the dielectric constant caused by the grating filter structure is expressed as: （9）； Performing Fourier transform on the rectangular function of equation (9) and taking the first order q=1, we can obtain: （9-1）； Where α is the duty cycle of the grating, which ranges from 0.01 to 0.

5. According to the mode orthogonal normalization condition, the coupling coefficient k of the uniform grating is obtained by combining equations (9) and (9-1), which is expressed as: （10）； Where △n is the refractive index modulation of the grating filter structure, Λ is the local chirp distribution, and λ B is the reflection center wavelength of the grating filter structure, that is, the Bragg wavelength, n eff is the average value of the effective refractive index of the grating filter structure; The relationship between the coupling coefficient k of the grating and the amplitude △a of the grating teeth is expressed by the empirical formula: （11）。 6. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 2, characterized in that: In step S3, the substrate integrated waveguide includes a dielectric substrate formed by a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a metal floor, and a side metal wall formed by two rows of metallized vias. The length L and width a of the waveguide for actual signal transmission are equal to the length L of the substrate integrated waveguide. SIW and width W SIW The equivalent relationship between them is: （12）； Wherein, d represents the diameter of the metallized via, p represents the distance between adjacent holes of the metallized via, and d and p satisfy the following relationship: d<p <2d(13-1); 0.05λ0<p<0.25λ0(13-2); Where λ0 is the center wavelength of the waveguide operating frequency.

7. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 6, characterized in that: In step S4, ΔL = a*beta, where beta is a constant with a value between 0.01 and 0.

5.

8. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 7, characterized in that: In step S5, the length L of the radiation slot array is calculated according to the lobe width and gain requirements, and the calculation formula is: （14）； Where, σ is the broadening factor of the Tailao line source; R0 is the ratio of the main lobe to the side lobe level; The Tailao line source broadening factor σ is determined by the following formula: （15）； in, It is the dividing point between the equal side lobe area and the unequal side lobe area of ​​the radiation pattern; A is determined by the ratio R0 of the level of the antenna main lobe and the side lobe: （16）； Then, the total number of slots N is calculated from the length L of the radiation slot array and the slot spacing Ls of the radiation slot array: N = (L / Ls) - 1 (17); The slot spacing Ls, slot length Lslot, and slot width Wslot of the radiation slot array satisfy the following relationship: Ls=2 / 3 (18-1); 200（18-2）； Lslot=0.96 / 2(18-3)。 9. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 8, characterized in that: The radiation slot array adopts a non-resonant waveguide slot array, the radiation slots are arranged longitudinally in the wide side direction of the waveguide, and adjacent radiation slots in the radiation slot array have a certain offset in the wide side direction of the waveguide, and the offset distance satisfies the Taylor weighted form.

10. The design method of the grating filter substrate integrated waveguide slot array antenna according to claim 9, characterized in that: When the radiation slot array satisfies the Taylor array, the excitation amplitude of each unit of the Taylor array is: （19）； Where: （20） ； （21）； After normalizing the excitation amplitude, the conductance value of each radiation gap is obtained by the following formula: （22）； Where P(p) is the power radiated per unit length of the slot, which is proportional to the square of the field distribution amplitude at that location; P0(p) is the input power in the waveguide, and p is the coordinate of the midpoint of the radiation slot; When the antenna input power is 1, the power absorbed by the terminal load is r, then: （23）； Thus, the conductivity value of each radiation gap can be obtained; When the conductance value of each radiating slot is determined, the normalized equivalent conductance of the broadside longitudinal resonant slot (23) is substituted into the following formula to calculate the distance x that each radiating slot deviates from the center line of the broadside of the waveguide: （24）； in, （25）， Right now, （26）。

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